1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly relates to a back-light module in an LCD.
2. Description of Related Art
Since an LCD has the advantages of low operating voltage, no radiation scattering, light weight, and small volume that cannot be achieved by a conventional cathode ray tube (CRT) display. Therefore, the LCD has become the major researching subject in the display field, and is continuously developed in the trend of colorization.
The LCD is a non-self-luminescent display, so the LCD needs a back-light module to provide a light beam to achieve the display function. In recent years, with the improvement of environmental protection awareness, the light-emitting device used in the back-light module adopts a light-emitting diode (LED) component to replace a cold cathode fluorescent lamp (CCFL). When the LED component is applied to the back-light module, for a side-view back-light module for example, the LED component is usually disposed on a bar-shaped printed circuit board to form an LED light bar. The LED light bar is usually electrically connected to a control circuit board through a flexible printed circuit (FPC).
FIG. 1 is a schematic top view of a light guide plate and an LED light bar in a conventional side-view back-light module. Referring to FIG. 1, the conventional side-view back-light module 100 includes a light guide plate 110 and a linear light source 120. The light guide plate has a top-emitting surface 112 and a side incident surface 114 connected to the top-emitting surface 112. The top-emitting surface 112 includes a peripheral area 112a and an effective illumination area 112b connected to the side incident surface 114. As shown in FIG. 1, the linear light source 120 is configured beside the side incident surface 114, and the linear light source 120 includes a circuit board 122 and a plurality of LED components 124. The LED components 124 are mounted on the circuit board 122 and are electrically connected to the circuit board 122.
As shown in FIG. 1, in the linear light source 120, a pitch between any two adjacent LED components 124 is P, and a shortest distance between the light-emitting surface of each LED component 124 and an edge of the effective illumination area 112b is A. To enable the brightness in the effective illumination area 112b to be uniform, the manufacturer determines an optimal A/P ratio according to a divergence angle α of the light beam of the LED component 124. However, currently, the LCD has been developed towards narrow frames. To meet the design requirement of narrow frames, the shortest distance A is inevitably reduced as required. When the A/P ratio is critically low, hot spots may appear in the effective illumination area 112b adjacent to the side incident surface 114. The shadow in FIG. 1 refers to the area with low brightness. The hot spots may be solved by reducing the pitch P, but when the pitch P is reduced, the manufacturer must use more LED components 124, which causes the increase of the cost.
Accordingly, it has become the subject in need of solution how to solve the hot spots caused by the low A/P ratio without increasing the number of the light-emitting devices and greatly increasing the manufacturing cost.